The present invention relates to an electric actuator mounted on a rotary valve, such as a ball valve, butterfly valve, etc., and to a fixing structure for detachably attaching the electric actuator to the rotary valve through a single touching action, which structure is applicable to a fixing structure for machine parts.
Actuators of this type are generally adapted to automatically open and close a valve with a structure in which a motor-driving shaft provided inside the actuator and a valve stem are connected directly or through a clutch mechanism. During power breakdown or in case of emergency, however, manual operation to open and close the valve is required.
Manual operation has heretofore been performed through a method of attaching a separate, manually operating shaft to a clutch mechanism, a method of projecting a motor-driving shaft from the upper or lower part of an actuator cover and using a tool to manually operate the projecting part of the motor-driving shaft, or a method of forming a hole in a motor-driving shaft and a projection on a valve stem, or vice versa, and inserting a tool into the hole to perform manual operation (see JP-A SHO 60-16074 (UM) and JP-A SHO 61-177266 (UM), for example).
On the other hand, there is a case where a valve or an actuator is generally provided with a flange or tapping seat as means for mounting the actuator on and connecting it to the shaft-mounting portion of the valve, and the actuator and shaft-mounting portion are fastened to each other with bolts or other such means (see JP-A SHO 54-92437 (UM), for example).
However, the conventional manually operating mechanisms for electrically operated actuators are complicated in structure and are large-sized in overall shape, and the manual operation is generally made using a tool to deteriorate operability. Therefore, demand is raised for development of electrically operated actuators that can solve the aforementioned problems. Since holes for bolts formed in a flange of an actuator of this type or valve have a slightly larger diameter than the bolt outside diameter in view of a fitting tolerance in relation to the bolts, when the bolts are loosened in attaching the actuator to or detaching it from the valve, there is a possibility of the actuator being shift by the amount of a gap between the bolts and the bolt holes. This fails to securely maintain the completely closed state when a rotary valve is required to completely close, resulting in a malfunction of the valve. In addition, when the flange is to be tapped, this requires an additional tapping work and necessitates a space for rotating and loosening the bolts in attaching or detaching the actuator and an operation tool, such as a wrench, screwdriver or other such means. Therefore, demand is also raised at the same time for development of a fixing configuration in the electrically operated actuator that can solve these problems.
The present invention has been developed in view of this state of affairs, and its object is to inexpensively provide a compact, electrically operated actuator simple in structure, light in weight and safe in operation. Another object is to provide an electrically operated actuator attachable to and detachable from a rotary valve by a single operation, and a fixing configuration for the actuator. A further object is to provide a fixing configuration for firmly fixing an electrically operated actuator with the rotational direction and axial direction of a rotary valve restrained, and a compact fixing structure capable of firmly fixing an electrically operated actuator with ease and applicable also to mechanical parts.
To attain the above objects, the present invention provides an electric actuator having inner component parts thereof inclusive of a motor covered by a cover main body. The cover main body has a coating (protection) function and serves as a manually operating part, and is equipped with a mechanism for switching between electrical and manual operations.
In the electric actuator of the invention, the cover main body is cylindrical and is provided on a disk-shaped base body on which the inner component parts inclusive of the motor are mounted, and the cover main body is made of a synthetic resin and has an outer face formed integrally with a fastening curved face so that the cover main body is capable of being gripped.
In the electric actuator of the invention, the switching mechanism comprises a fastening pin, an apex of which is elastically energized outward in a lateral part of a base body, and a fastening groove of an annular projection disposed on an inner peripheral face of the cover main body, the apex being separably fastened to the fastening groove. The annular projection is inserted into an annular groove formed in the lateral part of the base body to prevent the cover main body from being moved in a vertical direction relative to the base body.
In the electric actuator of the invention, the motor has a fastening projection, and the cover main body has a fastening depression formed on an inner peripheral face thereof, whereby an electrically operable state of the motor is established by causing the fastening projection to be engaged with the fastening depression and causing the apex of the fastening pin to be engaged with the fastening groove of the annular projection. The fastening projection of the motor is fixed in the fastening depression formed on the inner peripheral face of the cover main body, and the apex of the fastening pin engaged with the fastening groove of the annular projection is depressed to cancel the state of engagement, thereby rendering the cover main body manually rotatable in conjunction with the motor and parts attached to the motor.
In the electric actuator of the invention, the motor has a drive shaft to which a valve opening plate is fixed. The valve opening plate has a surface to which a display part is applied, the cover main body has an inspection window disposed therein, and the indicating part is adapted to be visually observed through the inspection window. The base body has an opening display piece fixed thereto, and the display part of the valve opening plate is positioned below the opening display piece to enable display on the opening display piece to be visually observed through the inspection window in the cover main body during manual operation of the electric actuator.
The electric actuator of the invention further comprises an interlock switch adapted to effect automatic interruption of supply of electricity to the motor during manual operation of the electric actuator. The interlock switch is disposed on the base body and has a working piece, the cover main body has a depression or a projection disposed on the inner peripheral face thereof, and the working piece is adapted to contact the depression or projection to induce operation of the interlock switch in consequence of rotation of the cover main body.
In the present invention, while an annular clutch is disposed in a gear tube of a rotary valve, the drive shaft of a motor having the lower end connected to the stem of the rotary valve is inserted into a fitting tube of a base body and, at the same time, the fitting tube is inserted into the clutch so as to restrain the rotation of the rotary valve and actuator.
In the invention, the clutch restrains the rotation of the rotary valve and actuator in one direction, and a stopper part disposed on the lateral face of the gear tube is made to collide with a colliding face formed on the base body of the actuator so as to restrain the rotation of the rotary valve and actuator in the other direction. In addition, a stopper pin mechanism disposed in the base body is fastened to the lower surface of a stopper part to prohibit the rotary valve and electric actuator from producing relative motion in the vertical direction.
According to the present invention, therefore, the cover main body manifests a coating (protection) function for ordinary actuators as well as a function of protecting inner parts of the actuator and preventing invasion of water, dust and the like. Furthermore, when gripped, the cover main body has a function of a handle for readily performing manual operation. Moreover, switching between electric and manual operations can be attained. For these reasons, it is possible to reduce the cost to a great extent and, since piping and assembling works or maintenance can be enhanced, further reduction in cost can be attained.
A conventional manual operation mechanism requires a large operation force because the manual operation is performed against the motor gear. However, according to the manual operation mechanism of the present invention, manual operation can be performed with a small operation force because the motor made integral with the drive shaft is manually operated via the cover main body.
Further, according to the present invention, an interlock mechanism actuates during manual operation of the actuator to prevent the motor from driving, thereby enabling risk prevention to provide an actuator excellent in safety.
Further, according to the present invention, the annular clutch mechanism is used to prevent the actuator from moving in the rotation direction, and the stopper pin mechanism is used to prevent the actuator from being extracted. Thus, the electric actuator can easily be attached or detached with one stroke.
According to another aspect of the present invention, there is provided a fixing structure for an electric actuator, wherein an annular one-way clutch structure is disposed at a fixing position for the rotary valve that is one of the constituent members. An annular face part is disposed at a fixing position for the electric actuator that is the other constituent member, and is inserted into the one-way clutch structure, thereby restraining the pair of constituent members from rotating one circumferential direction.
The invention further provides a fixing structure wherein the annular one-way clutch structure has a roller clutch structure, another fixing structure having a fastening mechanism provided on the rotary valve and electric actuator for restraining the rotation of the one-way clutch structure and restraining the opposite rotation thereof, and still another fixing structure using a stopper pin mechanism to restrain the rotary valve and electric actuator from moving in the axial direction.
According to the present invention, therefore, it is possible to reliably restrain the rotation direction when the constituent members are to be fixed, without a possibility of producing any deviation in the rotation direction. Moreover, since the number of processing and assembling steps is small, the cost can be reduced.
Furthermore, since the annular one-way clutch structure has a roller clutch structure, the overall structure can be made compact.
Thus, the compact, inexpensive structure is used to reliably restrain the rotation direction and axial direction, and the fixing operation can be effected with extreme ease.
Even for a pair of constituent members to which a rotation force is imparted, such as a fixing structure for a rotary valve and an electric actuator, it is possible to easily perform fixation in the rotation direction and vertical (axial) direction.
When applying this fixing structure to an electric actuator mounted on a rotary valve, the attachment and detachment thereof are easy to perform without the use of any tool. Moreover, the completely closing function in the rotary valve can be attained over a lone period of time. In addition, this fixing structure is applicable as fixing means for mechanical parts, thus attaining a wide range of applications.